Melanoma is a malignant tumor of melanocytes, cells that are derived from the neural crest. Although most melanomas arise in the skin, they may also arise from mucosal surfaces or at other sites to which neural crest cells migrate. Melanoma occurs predominantly in adults, and more than half of the cases arise in apparently normal areas of the skin. Early signs of malignant melanoma in a mole include darker or variable discoloration, itching, or an increase in size. Ulceration or bleeding are later signs. Melanoma can arise from any site on the skin surface.
Melanoma is generally diagnosed by a biopsy, preferably by local excision. Specimens are then examined by a pathologist to allow for microstaging. Studies show that distinguishing between benign pigmented lesions and early melanomas can be difficult, and even experienced dermatopathologists can have differing opinions.
Prognosis is affected by clinical and histological factors and by anatomic location of the lesion. Thickness and/or level of invasion of the melanoma, mitotic index, presence of tumor infiltrating lymphocytes, number of regional lymph nodes involved, and ulceration affect the prognosis. Patients who are younger, female, and who have melanomas on the extremities generally have a better prognosis.
If not treated, most melanomas eventually spread to other parts of the body. Melanomas rarely disappear without treatment (spontaneous regression) once they have spread. Metastatic melanoma usually cannot be cured. Early detection and removal of primary melanomas before they metastasize can prevent death from melanoma.
What is needed in the art are better methods for the early detection of melanoma. Preferred methods are non-invasive and able to detect melanomas before metastasis.